1. Field of Invention
The present invention relates to a chuck with a radially displaceable locking member, in particular, for a hammer drill for receiving a percussion drill.
2. Description of Prior Art
Working tools, which are driven by rotary percussion power tools, have a shank that is formlockingly received in a chuck of the power tool for rotation therewith, with a possibility of a limited axial displacement relative thereto. The shank is axially secured in the chuck with a radially displaceable locking member that penetrates into a groove formed in the shank and closed at its power tool side end.
German Publications DE 19724532 and DE 3205063 both disclose a chuck having a hollow cylindrical receiving sleeve having a predetermined guide diameter and a strip-shaped, rotation transmitting web projecting radially inward and having a predetermined web height, and a radially displaceable locking member. The rotation transmitting web extends from the receiving side, up to the receiving side edge of the sleeve opening, through which the locking member is radially displaced, over an axial length that approximately corresponds to the guide diameter of the receiving sleeve.
U.S. Pat. No. 4,107,949 discloses practically standardized shanks and associated chucks, which at present are primarily used worldwide with hammer drill systems. The shanks have a cylindrical guide surface with a guide diameter of 10 mm, locking grooves which are axially closed at their free end surface, and trapezoidal rotation transmitting grooves which are axially open at their free end surfaces. The associated chucks are provided with at least one, radially displaceable, locking member engageable in a locking groove and limiting the axial displacement of the shank, and thereby of the working tool, in the chuck. Two opposite rotation transmitting webs engage in respective rotation transmitting grooves of the shank and transmit a torque over respective tangential contact surfaces. These shanks were originally designed for drill diameters up to 17 mm and are, thus, associated with small low-power hammer drills with a power less than 650 W. With such power tool power-working tool combination wear problems were practically non-existent.
With the increase of power of the hand-held power tools, in particular, of hammer drills, in certain operational modes, high torques are transmitted to a working tool. Meanwhile, the practical application region of the hammer drills has expanded to drill diameters of 30 mm. It has been shown that a drill with a diameter above 17 mm leads to an increase wear and damage of the chuck in particular, to a noticeably high wear of the contact surfaces of the rotation transmitting webs. In particular, with modern, reinforcement-proof hammer drills, increased occurrences of a working tool blocking in a reinforced bore are observed. When the user wants to pull the hammer drill out of the bore, high torques are applied to the working tool, and high jerky tension forces are generated which are transmitted to the working tool by the receiving side edge of the receiving opening for the locking member.
These forces lead to breaking of the receiving sleeve in the vicinity of the receiving side edge when these forces exceed the allowable multi-axes tension.
Accordingly, an object of the present invention is a chuck for powerful hand-held power tool and having a reduced wear and susceptibility to being damaged.